The information posted here are not enough. You need to provide more details.

1. How many public folder databases?
2. When are you getting this error message?
a. Creating new database - ?
b. Creating new mailbox - ?

Things to Check:

Check the Address List - How many? and any empty/corrupted entries.

Check the address list policies for any issues.

Check any Domain controller in nested OU - it should be only under "Domain Controllers" OU --> Read from some forum

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cookd47Author Commented: 2016-11-03

Found Problem, Encrypto type Virus damaged files, Exchange still works, but damaged files will not allow changes. We had planned to migrate to a Hosted Exchange service, moved up schedule to this weekend